Plate keyer for radar transmitters



April 1952 W. M. ANDREW PLATE KEYER FOR RADAR TRANSMITTERS Filed Sept.7, 1945 gvwm WAR R EN M. ANDREW Patented Apr. 1,. 1952 UNITED STATESPATENT OFFICE (Granted under the act of March 3, 1883, as amended April30, 1928; 370 0. G. 757) 4 Claims.

This invention relates to a means for producing a sequential series ofhigh voltage pulses and more particularly to a means for pulse keyin anoscillator.

As is well known to those skilled in the art, numerous methods of andmeans for keying a pulse oscillator have been proposed by the prior art.This invention, however, relates primarily to a means for plate keying,incorporating a transformer and utilizing the inductiv swing of thesecondary thereof, caused by an abrupt interruption of current throughthe primary, to key the oscillator. More particularly this invention,for a given transformer, will produce pulses of greater peak power thanheretofore available.

It is an object of this invention to produce a sequential series of highvoltage impulses.

It is another object of this invention to provide a novel means forpulse keying an oscillator.

It is another object of this invention to provide a novel meansincorporating a transformer for plate keying a pulse oscillator.

Other objects and features of the present invention will become apparentupon a careful consideration of the followin description when takentogether with the accompanying drawings, the figures of which aredesigned for the express purpose of illustration and not as a definitionof the limits of the invention. Reference for the latter purpose is tobe had to the appended claims.

Fig. l is a schematic diagram partly in block of a preferred embodimentof the present; invention, and

Fig. 2 is a series of curves drawn to represent the various voltage waveforms developed at points along the circuit in Fig. 1 during a normaloperating cycle.

It is contemplated by the present invention to provide a means,incorporating a transformer, for producing a sequential series of highvoltage impulses across the secondary thereof, by intermittentlyinterrupting the current flow through the primary winding thereof. Moreparticularly to provide an electronic switch or keyer connected to theprimary winding of the transformer and having a means for augmenting thecurrent flow through the primary prior to the interruption of thecurrent.

Reference is had more particularly to Fig. 1 wherein there is shown apreferred embodiment of the present invention, comprisin the thermionicvacuum tube ll) of the four electrode type which is normally biased tocut-01f by way of a fixed bias supply, for example, connected acrossnected resistance l3.

the terminals II and II of the potentiometer 12 which in turn has thevariable arm thereof tied to the control electrode l 4 through aserially con- Tube I0 is sequentially rendered conducting through theapplication of a positive pulse to the control electrode l4, produced bythe keying circuit [5 which may be, for instance, a multivibrator or anyother suitable pulse generator, synchrcnized with a source ofalternating input potential applied at lead Hi. The coupling between thekeying circuit l5 and tube I0 is shown in the figure as a resistancecapacitance coupling circuit, but may be direct coupled if desired. Theoutput or plate I! of tube I0 is connected to a suitable source of highvoltage supply by way of the primary winding of an output transformerIS. The secondary of this transformer contains two separate windings,one of which F is loosely coupled to the primary and the other E, whichis nearly as possible a duplicate of the primary, is tightly coupled tothe primary. The loose coupled winding F is grounded at one end andconnected to the screen grid I 9 at the other end, while the output ofthe tight coupled winding E is tied to the plate, for example, of asuitable oscillator, not shown here.

A more complete understanding of the operation of the present inventionmay be had upon a careful consideration of the ensuing discussion. Itmust be remembered, however, that tube I0 is normally maintained blockedand that no current passes through the primary Winding of transformer l8during this period. Let it be assumed that the keying circuit [5 isdesigned, for example, to produce square wave pulses of the desired timelength and sequence and are synchronized with a given source ofalternating potential, say cycles for example, tied to lead It. Thusupon application of a positive pulse to control electrode I4, tube I0 isrendered conducting and current commences to flow through the primarywinding of the transformer l8. The keying pulses produced by the keyingcircuit l5 and applied to the control electrode M are shown more clearlyin curve A of Fig. 2. Thus as tube It passes current the plate voltageis driven negative on an exponential curve during the charging of theprimary winding as shown in curve B as extending from points a to b. Theoutput of the secondary winding E is connected in phase with the primaryand is, therefore, simultaneously driven negative in a like manner andamount with the primary. The output of the loose coupled secondary F,however, is connected degrees out of phase and, therefore, drives the2,59o,esc

undergo a high positive inductive swing as shown 1 in curve B asextending from points b to c. The loose coupled secondary F,however,'swings opin curve C. Thus as the secondary F drives the screengrid l9 positive from points 0 to d tube I0 is rendered conductingbetween the screen grid l9 and cathode 20 to dissipate the energy in thesecondary F and therefore damp oscillations as shown from points d' toe. During this time the secondary F also absorbs energy from the primarywinding and secondary winding E to damp their oscillatio'ns'as shownfrom points it to e;

It must be remembered that the voltage'wave forms shown in curve B applyto both the primary and secondary E swinging about the high voltagesupply in the primaryand ground in the 'secondary. Thus the efiectivevoltage applied to the plate of the oscillator, not shown here,'is asingle positely as shown extending from points I)" to c.-..

highvoltage pulse shown in curve D and having a timeleng'th-equal to thenatural period of the secondaryv E: It therefore 'becomes 'obvious thatthepulse lengthfcan be varied by simply using a variable tap transformerfor regulating the 'nat-' ural period? It also becomes obvious that bydriv ing the screen grid [9 positive during the negative excursion ofthe plate I'Tthereby causing tube ID to drawmore current allows the useof a smaller transformer for a given power'output than heretoforepossible.

Although I'haveshown and described only a certain andspecific embodimentof the present inventionI am fully aware of'the many modificationspossible thereof. Therefore this invention is not to berestricted,"except, insofar'as is necessitated by the prioriart and" thespirit of the appendedclaims; i

The invention described herein may be manufactured and'usednby or forthe Government of the United States of America forgovernmental purposeswithout'the payment of any royalties thereon or therefor.

I claim;

1. A means for producing aseries of high voltage impulses comprising, a'transformer having a primary winding, a first secondary winding, asecond secondary winding, and an output circuit tied across said secondsecondary, a'thermionic vacuumtube having an electron emittin cathode,an anode, a control'electrode, and a screen grid, a source of directcurrent voltage, said primary winding connecting said'anode to saiddirect current voltage, bias'means for blocking plate currentfiow'insaid tube, an impulse source coupled to the control electrode ofsaid tube for period'- ically rendering said tube conducting therebycausing intermittent current to flow through said primary winding, andmeans connecting the output'of said "first secondary to said screengrid, the-connection of said circuit secondary to said mar'ycurrentduring the unblocked period of said tube and subsequently damp toone cycle the inductive oscillation caused by the abrupt cessation ofsaid primary current upon reblocking said tube.

2. Means for producing high voltage impulse comprising a transformerhaving a primary winding and at least two secondary windings, one ofsaid secondary windings being relatively tightly coupled to the primarywinding and the other relatively loosely coupled to the primary winding,said one of said secondary windings serving to provide an outputconnection across which an output pulse may be derived, a normallynon-conducting electron discharge device including anode, cathode,control and screen electrodes, the space discharge path provided by theanode and cathode electrodes of said tube being connected in series withthe primary winding of said transformer, a source' 'of direct currentpotential connected across said series'connection, means operative tomomentarily render said electron discharge device conducting to therebyestablish and terminate a current flow through said primary windingwhereby inductive oscillations are produced in said transformer, andmeans coupling, the output of the other of said secondary windings tothe screen electrode of said tube, said other secondary winding beingpoled to augment current flow through said discharge device during theconduction of said tube and to dissipate the energy stored in saidtransformer at the conclusion of the'first half cycle of said inductiveoscillations.

3. An impulse'generator comprising an inductive winding, an electrondischarge device having anode-cathode, controlandscre'en' gridelectrodes, a source'of'plate supply voltage connected to said windingand the anode cathode discharge path of said device in series, biasmeans connected between the control and cathode electrodes of saiddevice for holding said device non-conducting, an impulsesource'coupledto the control electrode to establish momentary conduction in saiddevice to thereby produce an inductive oscillation in said winding, andmeans coupling said inductive oscillation to the screen grid of saiddevice in such phase as to augment the current flow through said deviceduring conduction thereof.

4. An impulse generator comprising an inductive winding, an electrondischarge device having anode, cathode, control and screen gridelectrodes, a source of plate supply voltage connected to said windingand the anode cathode discharge path of said device in series, biasmeans connected between the control and' cathode electrodes of saiddevice for holdin said device non-conducting, means coupled to thecontrol electrode to establish momentary conduction in said device tothereby produce an inductive oscillation in said winding, and meanscoupling said inductive oscillation to the screen grid of said device insuch phase a's to' augment the current fiow through said device duringconduction thereof.

WARREN M. ANDREW.

REFERENCES CITED flhe'following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,587,520 Hartley June 8, 19261,733,614 Marrison Oct. 29, 1929 2,059,683 Farnsworth Nov. 3, 19362,196,825 Geiger- Apr. 9, 1940

